Mechanistic investigation has been carried out for the reaction between Rh(tmp) and the nitroxide, 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO). Mechanistically, Rh(tmp) at first coordinated with one molecule of TEMPO to produce a 1:1 adduct. Through this complex, parallel major carbon-carbon bond activation (CCA) and minor carbon-hydrogen bond activation (CHA) occurred. CCA was more favorable at higher reaction temperatures. The CHA product Rh(tmp)H further reacted with excess TEMPO to produce Rh(tmp) again for further CCA and CHA. The overall activation reaction was found to follow second order kinetics, rate = k [Rh(tmp)] [TEMPO]. / Rhodium(II) meso-tetramesitylporphyrin (Rh(tmp)) has been prepared successfully by photolysis of Rh(tmp)Me under anaerobic conditions at low temperature. / The activation of carbon-carbon bond with high reactivity and selectivity has attracted many organometallic chemists due to its fundamental importance in basic chemical research and potential utility in organic synthesis. / The aliphatic, unstrained carbon-carbon bonds of a series of nitroxides 1,1,3,3-tetraalkylisoindolin-2-oxyl have been activated by Rh(tmp). In long chain alkyl substituted nitroxides, regioselective carbon-carbon bond activations were observed. This was attributed to the cooperative effects of the bond dissociation energy and the steric hindrance of alkyl groups in nitroxides. While PPh3 was used as the fifth ligand, the yields of regioselective CCA changed. For sterically less hindered nitroxides, the total yield of CCA increased. For sterically more hindered nitroxides, the total yield of CCA decreased. These can be attributed to the cooperation of steric and electronic effects in the rhodium porphyrin complexes and nitroxides. / The C(sp3)-C(sp3) bonds of a series of alpha-alkylphenylacetonitriles have been activated by Rh(tmp) using PPh3 as the optimized fifth ligand. The activation was not regioselective. The CCA yield was affected by bond energy and steric hindrance of the nitriles. The optimal reaction temperature was 130 °C. / Under same reaction conditions, CCA between Rh(tmp) and 2-alkylbenzonitriles also was carried out. Only C(sp3)-C( sp3) bond was activated. CCA yield depended on the BDE of C-C bond in alkyl substituents. / by Li Xinzhu. / "June 2006." / Adviser: Kin Shing Chan. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6396. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 197-210). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_343726 |
| Date | January 2006 |
| Contributors | Li, Xinzhu., Chinese University of Hong Kong Graduate School. Division of Chemistry. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, theses |
| Format | electronic resource, microform, microfiche, 1 online resource (x, 283 p. : ill.) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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